Adds clear to levelup + updates tests (#40792)

* feat: adds clear to levelup

Signed-off-by: Carson Farmer <carson.farmer@gmail.com>

* docs: update contributors

Signed-off-by: Carson Farmer <carson.farmer@gmail.com>

types/levelup/index.d.ts

@@ -1,7 +1,8 @@
-// Type definitions for levelup 3.1
+// Type definitions for levelup 4.3
 // Project: https://github.com/Level/levelup
 // Definitions by: Meirion Hughes <https://github.com/MeirionHughes>
 //                 Daniel Byrne <https://github.com/danwbyrne>
+//                 Carson Farmer <https://github.com/carsonfarmer>
 // Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
 // TypeScript Version: 2.8
 
@@ -25,6 +26,11 @@ type LevelUpDel<K, O> =
     ((key: K, options: O, callback: ErrorCallback) => void) &
     ((key: K, options?: O) => Promise<void>);
 
+type LevelUpClear<O> =
+    ((callback: ErrorCallback) => void) &
+    ((options: O, callback: ErrorCallback) => void) &
+    ((options?: O) => Promise<void>);
+
 type LevelUpBatch<K, O> =
     ((key: K, callback: ErrorCallback) => void) &
     ((key: K, options: O, callback: ErrorCallback) => void) &
@@ -45,6 +51,20 @@ type InferDBDel<DB> =
     LevelUpDel<K, O> :
     LevelUpDel<any, AbstractOptions>;
 
+type InferDBClear<DB> =
+    DB extends { clear: (options: infer O, callback: ErrorCallback) => void } ?
+    LevelUpClear<O> :
+    LevelUpClear<AbstractClearOptions>;
+
+interface AbstractClearOptions<K = any> extends AbstractOptions {
+    gt?: K;
+    gte?: K;
+    lt?: K;
+    lte?: K;
+    reverse?: boolean;
+    limit?: number;
+}
+
 export interface LevelUp<DB = AbstractLevelDOWN, Iterator = AbstractIterator<any, any>> extends EventEmitter {
     open(): Promise<void>;
     open(callback?: ErrorCallback): void;
@@ -54,6 +74,7 @@ export interface LevelUp<DB = AbstractLevelDOWN, Iterator = AbstractIterator<any
     put: InferDBPut<DB>;
     get: InferDBGet<DB>;
     del: InferDBDel<DB>;
+    clear: InferDBClear<DB>;
 
     batch(array: AbstractBatch[], options?: any): Promise<void>;
     batch(array: AbstractBatch[], options: any, callback: (err?: any) => any): void;
@@ -82,6 +103,10 @@ export interface LevelUp<DB = AbstractLevelDOWN, Iterator = AbstractIterator<any
     */
     on(event: 'batch', cb: (ary: any[]) => void): this;
     /*
+    emitted when clear is called
+    */
+    on(event: 'clear', cb: (opts: any) => void): this;
+    /*
     emitted on given event
     */
     on(event: 'open' | 'ready' | 'closed' | 'opening' | 'closing', cb: () => void): this;

types/levelup/levelup-tests.ts

@@ -68,3 +68,11 @@ db.createReadStream()
     .on('end', () => {
       console.log('Stream closed');
     });
+
+db.clear((error) => {
+});
+
+db.clear({ gt: 'hello' }, (error) => {
+});
+
+db.clear().then(() => console.log('cleared'));